Study On Seismic Performance Of Continuous Beam Bridge With High Hollow Pier In Mountainous Railway

Long-span continuous girder bridge has strong site adaptability,mature construction method and high stiffness.The advantages of small deformation and good seismic performance occupy a large proportion in railway bridges in the western part of China.Because of its complex terrain,large-span continuous girder bridges often cross valleys and rivers in the form of high piers in western mountainous areas,while most of them are located in high-intensity seismic areas.It is necessary to study the seismic performance of hollow high piers.However,at present,there are few studies on hollow high piers of railway in mountainous areas,especially the influence of structural parameters on seismic performance is irregular.Based on this background,it is necessary to study the seismic performance of hollow high piers.In this paper,a hollow high pier long-span bridge on Chengdu-Kunming Railway is taken as the research object,and the seismic performance of the bridge structure is studied.The full bridge model is established by using the large-scale finite element program Midas Civil.The natural vibration characteristics of hollow piers with three different cross-sections,rectangular,circular and circular end,are analyzed and calculated.Response spectrum method and time history analysis method are used to analyze the internal force and displacement response of the bridge under earthquake action.The results of response spectrum method and time history analysis method are compared and verified.The dynamic response of the bridge is analyzed and summarized.When time history analysis method is used to calculate,this paper innovatively adopts three principles method to select seismic wave.The input seismic wave is basically consistent with the site condition of the bridge,and the effective peak acceleration of the seismic wave is consistent with the response spectrum method,which can ensure the accuracy of the calculation results.This paper also analyzes the influence of pier height on the seismic performance of bridges,and establishes five bridge models of 50 m,60m,70 m,80m and 90 m for comparison.The seismic response of bridges is calculated by time history analysis method,and the seismic performance of hollow high pier railway bridges under different pier heights is studied.This paper also makes a comparative analysis of the section of hollow high piers.By comparing the circular end hollow section,rectangular hollow section and circular hollow section,the influence of the axial compression ratio,concrete strength and reinforcement ratio on the ductility and seismic resistance of piers is analyzed.It is concluded that the seismic performance of circular end piers is better,while that of rectangular piers is weaker.At present,rectangular piers are seldom used in new railways.